Methods and apparatus for calibrating programmable material consolidation apparatus

ABSTRACT

A programmed material consolidation apparatus includes at least one fabrication site and a material consolidation system associated with the at least one fabrication site. The at least one fabrication site may be configured to receive one or more fabrication substrates, such as semiconductor substrates. A machine vision system with a translatable or locationally fixed camera may be associated with the at least one fabrication site and the material consolidation system. A cleaning component may also be associated with the at least one fabrication site. The cleaning component may share one or more elements with the at least one fabrication site, or may be separate therefrom. The programmed material consolidation apparatus may also include a substrate handling system, which places fabrication substrates at appropriate locations of the programmed material consolidation apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/705,394,filed Nov. 10, 2003, pending, which claims the benefit of U.S.Provisional Application No. 60/425,567, filed Nov. 11, 2002, thedisclosure of which is hereby incorporated in its entirety by thisreference. This application is also related to U.S. application Ser. No.10/705,249, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,250, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,405, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,409, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,726, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,728, filed Nov. 10, 2003, pending, to U.S. application Ser. No.10/705,729, filed Nov. 10, 2003, pending, and to U.S. application Ser.No. 10/705,730, filed Nov. 10, 2003, pending. The disclosure of each ofthe previously referenced U.S. patent applications is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to apparatus for effectingprogrammed material consolidation techniques, such as stereolithography,and, more particularly, to apparatus that are configured to fabricatefeatures on semiconductor devices and related components. The presentinvention also relates to programmed material consolidation methods thatinclude use of such apparatus.

2. Background of Related Art

Over the past decade or so, a manufacturing technique which has becomeknown as “stereolithography” and which is also known as “layeredmanufacturing” has evolved to a degree where it is employed in manyindustries.

Basically, stereolithography, as conventionally practiced, involvesutilizing a computer, typically under control of three-dimensional (3D)computer-aided design (CAD) software, to generate a 3D mathematicalsimulation or model of an object to be fabricated. The computermathematically separates or “slices” the simulation or model into alarge number of relatively thin, parallel, usually verticallysuperimposed layers. Each layer has defined boundaries and otherfeatures that correspond to a substantially planar section of thesimulation or model and, thus, of the actual object to be fabricated. Acomplete assembly or stack of all of the layers defines the entiresimulation or model. A simulation or model which has been manipulated inthis manner is typically stored and, thus, embodied as a CAD computerfile. The simulation or model is then employed to fabricate an actual,physical object by building the object, layer by superimposed layer.Surface resolution of the fabricated object is, in part, dependent uponthe thickness of the layers.

A wide variety of approaches to stereolithography by different companieshas resulted in techniques for fabricating objects from various types ofmaterials. Regardless of the material employed to fabricate an object,stereolithographic techniques usually involve disposition of a layer ofunconsolidated or unfixed material corresponding to each layer of thesimulation or model. Next, the material of a layer is selectivelyconsolidated or fixed to at least a partially consolidated, partiallyfixed, or semisolid state in those areas of a given layer thatcorrespond to solid areas of the corresponding section of the simulationor model. Also, while the material of a layer is being consolidated orfixed, that layer may be bonded to a lower layer of the object which isbeing fabricated.

The unconsolidated material employed to build an object may be suppliedin particulate or liquid form. The material may itself be consolidatedor fixed. Alternatively, when the unconsolidated material comprisesparticles, a separate binder material mixed therein or coating theparticles may facilitate bonding of the particles to one another, aswell as to the particles of a previously formed layer.

Surface resolution of the features of a fabricated object depends, atleast in part, upon the material being used. For example, whenparticulate materials are employed, resolution of object surfaces ishighly dependent upon particle size, whereas when a liquid is employed,surface resolution is highly dependent upon the minimum surface area ofthe liquid which can be consolidated or fixed and the minimum thicknessof a material layer that can be generated. Of course, in either case,resolution and accuracy of the features of an object being produced fromthe simulation or model are also dependent upon the ability of theapparatus used to consolidate or fix the material to precisely track themathematical instructions indicating solid areas and boundaries for eachlayer of material.

Toward that end, and depending upon the type and form of material to befixed, stereolithographic fabrication processes have employed variousfixation approaches. For example, particles have been selectivelyconsolidated by particle bombardment (e.g., with electron beams),disposition of a binder or other fixative in a manner similar to ink-jetprinting techniques, and focused irradiation using heat or specificwavelength ranges. In some instances, thin, preformed sheets of materialmay be superimposed to build an object, each sheet being fixed to anext-lower sheet and unwanted portions of each sheet removed, a stack ofsuch sheets defining the completed object.

Early on in its development, stereolithography was used to rapidlyfabricate prototypes of objects from CAD files. Prototypes of objectsmight be built to verify the accuracy of the CAD file defining theobject (e.g., an object or negative of a mold to be machined) and todetect any design deficiencies and possible fabrication problems beforea design was committed to large-scale production. Stereolithographictechniques have also been used in the fabrication of molds. Usingstereolithographic techniques, either male or female forms on which moldmaterial might be disposed could be rapidly generated.

In more recent years, stereolithography has been employed to develop andrefine object designs in relatively inexpensive materials.Stereolithography has also been used to fabricate small quantities ofobjects for which the cost of conventional fabrication techniques isprohibitive, such as in the case of plastic objects that haveconventionally been formed by injection molding techniques. It is alsoknown to employ stereolithography in the custom fabrication of productsgenerally built in small quantities or where a product design isrendered only once. Finally, it has been appreciated in some industriesthat stereolithography provides a capability to fabricate products, suchas those including closed interior chambers or convoluted passageways,which cannot be fabricated satisfactorily using conventionalmanufacturing techniques. It has also been recognized in some industriesthat a stereolithographic object or component may be formed or builtaround another, pre-existing object or component to create a largerproduct.

Conventionally, stereolithographic apparatus have been used to fabricatefreestanding structures. Such structures have been formed directly on aplaten or other support system of the stereolithographic fabricationapparatus, which is located within the fabrication tank of thestereolithographic apparatus. As the freestanding structures arefabricated directly on the support system, there is typically no need toprecisely and accurately position features of the stereolithographicallyfabricated structure. As such, conventional stereolithographic apparatuslack machine vision systems for ensuring that structures are fabricatedat certain locations.

Moreover, conventional stereolithographic apparatus lack supportsystems, handling systems, and cleaning equipment which are suitable foruse with relatively delicate structures, such as semiconductorsubstrates and semiconductor devices that have been fabricated thereon.

Accordingly, there is a need for stereolithography apparatus which areconfigured to form structures on fabrication substrates, such assemiconductor substrates and semiconductor device components and whichinclude systems for accurately positioning the fabricated structures,supporting and handling the fabrication substrates, and cleaning excessand residual material from the fabrication substrates.

SUMMARY OF THE INVENTION

The present invention includes stereolithography apparatus and otherprogrammable material consolidation apparatus and systems that areconfigured to fabricate features on semiconductor devices or oncomponents that are configured for use with semiconductor devices. Inaddition, the present invention includes stereolithographic and otherprogrammed material consolidation methods (e.g., stereolithography,layered object manufacturing (LOM), selective laser sintering (SLS),photopolymer jetting, selective particle atomization and consolidation(laser engineered net shaping, or “LENS”), and other so-called “rapidprototyping” technologies) that include use of apparatus according tothe present invention. As used herein, the term “stereolithography” andvariations thereof, where applicable, are intended to denote all typesof programmed material consolidation techniques and is used synonymouslywith the phrase “programmed material consolidation” and variationsthereof.

A programmed material consolidation apparatus, or “stereolithographyapparatus” for simplicity, according to the present invention includes afabrication tank, which is also referred to herein as a “fabricationchamber” or even more broadly as a “fabrication site.” The fabricationtank includes a platen or other support system suitable for carryingsubstrates upon which structures are to be stereolithographicallyfabricated, which may also be termed “fabrication substrates.” By way ofexample only, the fabrication tank and the support therein may be sizedand configured to receive one or more semiconductor substrates, each ofwhich carries a plurality of semiconductor devices. Alternatively, or inaddition, the platen or other support system may be configured tosupport freestanding structures as they are fabricated. In addition, thefabrication tank may include a reservoir that is configured to hold avolume of unconsolidated material, such as a liquid polymer.

A material consolidation system is associated with the fabrication tankin such a way as to direct consolidating energy (e.g., in the form ofradiation, such as a laser beam or less-focused radiation) to a surfaceof the quantity of unconsolidated material within the reservoir of thefabrication tank. When selective consolidation is desired, a high levelof precision may be achieved when the consolidating energy is focusedand the surface of the quantity of unconsolidated material and the focalpoint for the consolidating energy substantially intersect one another.

Optionally, a stereolithography apparatus that incorporates teachings ofthe present invention may include a machine vision system. The machinevision system includes an optical detection element, such as a camera,as well as a controller or processing element, such as a computerprocessor or a collection of computer processors, associated with theoptical detection element. The optical detection element may bepositioned in a fixed location relative to the fabrication tank orconfigured to move relative to the fabrication tank.

When included as part of a stereolithographic apparatus thatincorporates teachings of the present invention, the optical detectionelement of a machine vision system is useful for identifying thelocations of recognizable features, including, without limitation,features on a fabrication substrate and features, such as fiducialmarks, at a fabrication site. For example, the optical detection elementmay be configured and/or located to “see” relatively large structures,such as those that can be seen by the naked eye (i.e., macroscopicstructures), such as the locations of semiconductor devices upon afabrication substrate. Alternatively, or in addition, the opticaldetection element may be configured and/or located to “see” very small,even microscopic structures.

Another optional feature of a stereolithographic apparatus of thepresent invention is a cleaning component. A cleaning component may bepositioned and configured to remove excess liquid polymer from afabrication substrate while the fabrication substrate remains positionedupon a support system that is associated with the fabrication tank. Sucha cleaning component may comprise at least a part of the fabricationtank and, thus, operate prior to introduction of another fabricationsubstrate into the fabrication tank. Alternatively, excess liquidpolymer may be removed from a fabrication substrate during or followingremoval thereof from the fabrication tank.

Additionally, a stereolithographic apparatus that incorporates teachingsof the present invention may include a material reclamation system. Thematerial reclamation system may be associated with one or both of thefabrication tank and a cleaning component, if the stereolithographicapparatus includes a cleaning component. By way of example, the materialreclamation system may collect material from the cleaning component andrecycle the same into the fabrication tank.

A programmed material consolidation system that incorporates teachingsof the present invention may include a plurality of fabrication sitesand share a common material consolidation system, machine vision system,handling system, cleaning component, or material reclamation system.

The present invention also includes methods for calibratingstereolithographic apparatus that incorporate teachings of the presentinvention. For example, the locations at which unconsolidated materialmay be selectively consolidated may be calibrated with a machine visionsystem. As another example, the magnification of a machine vision systemmay be calibrated. Also, a material consolidation system of astereolithographic apparatus according to the present invention may becalibrated to optimize the linearity with which selectivelyconsolidating energy impinges on a surface of unconsolidated material.

Programmed material consolidation fabrication processes, includingmethods of using each of the features described herein, are also withinthe scope of the present invention. In particular, stereolithographicfabrication processes that incorporate teachings of the presentinvention include the use of stereolithographic techniques to fabricatefeatures on another structure, or fabrication substrate, such as asemiconductor substrate or semiconductor device component (e.g., a leadframe, a circuit board, etc.).

Other features and advantages of the present invention will becomeapparent to those of skill in the art through consideration of theensuing description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which depict exemplary embodiments of various featuresof the present invention:

FIG. 1 is a schematic representation of various possible elements of astereolithographic apparatus for fabricating features on semiconductordevices or associated components in accordance with the presentinvention, the elements including a fabrication tank, a materialconsolidation system, a machine vision system, a cleaning component, anda material reclamation system;

FIG. 2 schematically depicts an exemplary stereolithographic apparatusin which a single material consolidation system and/or a single machinevision system may be shared by a plurality of fabrication tanks;

FIG. 3 schematically depicts an exemplary embodiment of fabrication tankthat may be used in a stereolithographic apparatus of the presentinvention, the fabrication tank including a cavity and a reservoir whichare continuous with one another;

FIG. 3A illustrates an exemplary support element of the fabrication tankof FIG. 3, which support element has a substantially planar supportsurface;

FIG. 3B shows another exemplary support element of the fabrication tankshown in FIG. 3, which support element includes recesses formed in thesupport surface thereof;

FIG. 3C illustrates an exemplary volume control element of thefabrication tank depicted in FIG. 3, which volume control element isconfigured to add unconsolidated material to and/or removeunconsolidated material from the reservoir of the fabrication tank;

FIG. 3D depicts another exemplary volume control element of thefabrication tank of FIG. 3, which volume control element is configuredto displace unconsolidated material located within the reservoir of thefabrication tank;

FIG. 3E schematically depicts a stereolithographic fabrication tankwhich includes another variation of volume control and surface levelcontrol element;

FIG. 4 schematically depicts another embodiment of fabrication tank thatincludes a rotatable support element and which may be used in astereolithographic apparatus according to the present invention, such asthose shown in FIGS. 1 and 2, which fabrication tank also comprises acleaning component and a material reclamation system;

FIG. 4A is a top view of an example of a retention system for use with asupport system of the fabrication tank of FIG. 4;

FIG. 4B is a cross-section taken along line 4B-B of FIG. 4A;

FIG. 4C is a top view of another example of a retention system for usewith a support system of the fabrication tank of FIG. 4;

FIG. 4D is a cross-section taken along line 4D-4D of FIG. 4C;

FIG. 4E is a cross-sectional representation of another embodiment ofsupport system that may be used in a fabrication tank of a semiconductorfabrication apparatus according to the present invention;

FIG. 4F is a top view of the support system shown in FIG. 4E;

FIG. 5 is a schematic representation of still another exemplaryembodiment of fabrication tank that incorporates teachings of thepresent invention;

FIG. 6 is a schematic representation of an exemplary embodiment of amaterial consolidation system according to the present invention, whichis configured to focus consolidating energy so as to selectivelyconsolidate unconsolidated material which has been placed over afabrication substrate;

FIG. 7 schematically depicts another exemplary embodiment of materialconsolidation system, which is configured to generally consolidateunconsolidated material which has been placed over a fabricationsubstrate;

FIG. 8 schematically illustrates an exemplary embodiment of machinevision system that may be used with a fabrication tank of astereolithographic apparatus according to the present invention, withthe machine vision system being configured to move relative to a surfaceof unconsolidated material which is to be consolidated by thestereolithographic apparatus;

FIG. 9 is a schematic representation of another exemplary embodiment ofmachine vision system, which embodiment is configured to remain at afixed location relative to a surface of unconsolidated material which isto be consolidated by a stereolithographic apparatus with which themachine vision system is used;

FIG. 10 is a schematic representation of another embodiment of cleaningcomponent, as well as an exemplary embodiment of a material reclamationsystem;

FIG. 11 is a schematic representation of yet another embodiment ofcleaning component that may be used as part of a stereolithographicapparatus according to the present invention;

FIG. 12 is a schematic representation of the manner in which thelocations at which a layer of unconsolidated material is selectivelyconsolidated may be calibrated with a machine vision system of astereolithographic apparatus of the present invention;

FIG. 13 is a top view of a fabrication tank, depicting an exemplarymanner in which a linearity calibration may be conducted; and

FIG. 14 is a cross-sectional representation of a fabrication substrateand an object being stereolithographically fabricated thereon inaccordance with teachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary stereolithographic apparatus 10 for fabricating features onsemiconductor substrates 52, semiconductor devices 54 or associatedcomponents (e.g., lead frames, circuit boards, etc.) (not shown) orother fabrication substrates 50 is schematically depicted in FIG. 1. Asshown, stereolithographic apparatus 10 includes a fabrication tank 100and a material consolidation system 200, a machine vision system 300, acleaning component 400, and a material reclamation system 500 that areassociated with fabrication tank 100. The depicted stereolithographicapparatus 10 also includes a substrate handling system 600, such as arotary feed system or linear feed system available from GenmarkAutomation Inc., of Sunnyvale, California, for moving fabricationsubstrates 50 from one system of stereolithographic apparatus toanother. Features of one or more of the foregoing systems may beassociated with one or more controllers 700, or processing elements,such as computer processors or smaller groups of logic circuits, in sucha way as to effect their operation in a desired manner.

Controller 700 may comprise a computer or a computer processor, such asa so-called “microprocessor,” which may be programmed to effect a numberof different functions. Alternatively, controller 700 may be programmedto effect a specific set of related functions or even a single function.Each controller 700 of stereolithographic apparatus 10 may be associatedwith a single system thereof or a plurality of systems so as toorchestrate the operation of such systems relative to one another.

Fabrication tank 100 includes a chamber 110 which is configured tocontain a support system 130. In turn, support system 130 is configuredto carry one or more fabrication substrates 50. By way of example only,the types of fabrication substrates 50 that support system 130 may beconfigured to carry may include, without limitation, a bulksemiconductor substrate 52 (e.g., a full or partial wafer ofsemiconductive material, such as silicon, gallium arsenide, indiumphosphide, a silicon-on-insulator (SOI) type substrate, such assilicon-on-ceramic (SOC), silicon-on-glass (SOG), or silicon-on-sapphire(SOS), etc.) that includes a plurality of semiconductor devices 54thereon.

Fabrication tank 100 may also have a reservoir 120 associated therewith.Reservoir 120 may be continuous with chamber 110. Alternatively,reservoir 120 may be separate from, but communicate with, chamber 110 insuch a way as to provide unconsolidated material 126 thereto. Reservoir120 is configured to at least partially contain a volume 124 ofunconsolidated material 126, such as a photoimageable polymer, or“photopolymer,” particles of thermoplastic polymer, resin-coatedparticles, or the like.

Photopolymers believed to be suitable for use with a stereolithographicapparatus 10 according to the present invention include, withoutlimitation, ACCURA® SI 40 Hc and AR materials, ACCURA® SI 40 NDmaterial, and CIBATOOL SL 5170, SL 5210, SL 5530, and SL 7510 resins.The ACCURA® materials are available from 3D Systems, Inc., of Valencia,Calif., while the CIBATOOL resins are available from Ciba SpecialtyChemicals Inc., of Bezel, Switzerland.

Reservoir 120 or another component associated with one or both offabrication tank 100 and reservoir 120 thereof may be configured tomaintain a surface 128 of a portion of volume 124 located within chamber110 at a substantially constant elevation relative to chamber 110.

A material consolidation system 200 is associated with fabrication tank100 in such a way as to direct consolidating energy 220 into chamber 110thereof, toward at least areas of surface 128 of volume 124 ofunconsolidated material 126 within reservoir 120 that are located overfabrication substrate 50. Consolidating energy 220 may comprise, forexample, electromagnetic radiation of a selected wavelength or a rangeof wavelengths, an electron beam, or other suitable energy forconsolidating unconsolidated material 126. Material consolidation system200 includes a source 210 of consolidating energy 220. If consolidatingenergy 220 is focused, source 210 or a location control element 212associated therewith (e.g., a set of galvanometers, including one forx-axis movement and another for y-axis movement) may be configured todirect, or position, consolidating energy 220 toward a plurality ofdesired areas of surface 128. Alternatively, if consolidating energy 220remains relatively unfocused, it may be directed generally towardsurface 128 from a single, fixed location or from a plurality ofdifferent locations. In any event, operation of source 210, as well asmovement thereof, if any, may be effected under the direction ofcontroller 700.

When material consolidation system 200 directs focused consolidatingenergy 220 toward surface 128 of volume 124 of unconsolidated material126, stereolithographic apparatus 10 may also include a machine visionsystem 300. Machine vision system 300 facilitates the direction offocused consolidating energy 220 toward desired locations of features onfabrication substrate 50. As with material consolidation system 200,operation of machine vision system 300 may be proscribed by controller700. If any portion of machine vision system 300, such as a camera 310thereof, moves relative to chamber 110 of fabrication tank 100, thatportion of machine vision system 300 may be positioned so as provide aclear path to all of the locations of surface 128 that are located overeach fabrication substrate 50 within chamber 110.

Optionally, as schematically depicted in FIG. 2, one or both of materialconsolidation system 200 (which may include a plurality of mirrors 214)and machine vision system 300 of a stereolithographic apparatus 10′ maybe oriented and configured to operate in association with a plurality offabrication tanks 100. Of course, one or more controllers 700 would beuseful for orchestrating the operation of material consolidation system200, machine vision system 300, and substrate handling system 600relative to a plurality of fabrication tanks 100.

With returned reference to FIG. 1, cleaning component 400 ofstereolithographic apparatus 10 may also operate under the direction ofcontroller 700. Cleaning component 400 of stereolithographic apparatus10 may be continuous with a chamber 110 of fabrication tank 100 orpositioned adjacent to fabrication tank 100. If cleaning component 400is continuous with chamber 110, any unconsolidated material 126 thatremains on a fabrication substrate 50 may be removed therefrom prior tointroduction of another fabrication substrate 50 into chamber 110.

If cleaning component 400 is positioned adjacent to fabrication tank100, residual unconsolidated material 126 may be removed from afabrication substrate 50 as fabrication substrate 50 is removed fromchamber 110. Alternatively, any unconsolidated material 126 remaining onfabrication substrate 50 may be removed therefrom after fabricationsubstrate 50 has been removed from chamber 110, in which case thecleaning process may occur as another fabrication substrate 50 ispositioned within chamber 110.

Material reclamation system 500 collects excess unconsolidated material126 that has been removed from a fabrication substrate 50 by cleaningcomponent 400, then returns the excess unconsolidated material 126 toreservoir 120 associated with fabrication tank 100.

Fabrication Sites

Turning now to FIGS. 3-5, various exemplary embodiments of fabricationsites, chambers, or tanks, that may be used in a stereolithographicapparatus 10 (FIG. 1) or other programmable material consolidationapparatus or system that incorporates teachings of the present inventionare illustrated.

FIG. 3 shows a fabrication tank 100′ which includes a chamber 110′ thatis continuous with a reservoir 120′. A support system 130′, whichincludes a platen, or support element 132′, a positioning element 140′,and an actuation element 146′, is located within reservoir 120′, beneathchamber 110′, and may be moved to a plurality of different verticalpositions, or elevations, therein.

A substrate-supporting surface of support element 132′, which is alsoreferred to herein as a support surface 134′ for the sake of simplicity,may be substantially planar, as shown in FIG. 3A. Alternatively, asdepicted in FIG. 3B, support surface 134′ may have one or more recesses136′ formed therein, each recess 136′ being configured to receive atleast a portion of a fabrication substrate 50. Additionally, each recess136′ may be configured to position a fabrication substrate 50 in adesired orientation upon introduction of the same thereinto. Supportsurface 134′ may be configured to carry a single fabrication substrate50 or a plurality of fabrication substrates 50.

Positioning element 140′ may be coupled to a bottom surface 138′ ofsupport element 132′ or otherwise operatively associated with supportelement 132′. Positioning element 140′ is depicted as being an elongatestructure that includes a coupling end 142′ that has been secured tobottom surface 138′, as well as an opposite, actuation end 144′.Nonetheless, positioning elements 140′ of other configurations are alsowithin the scope of the present invention. By way of example only,positioning element 140′ may comprise a hydraulically or pneumaticallyactuated piston, a screw, a linear actuator or stepper element, a seriesof gears, or the like.

Actuation element 146′ is, of course, associated with and configured toeffect movement of positioning element 140′. Accordingly, examples ofactuation elements 146′ that may be used as part of support system 130′include, but are not limited to, hydraulic actuators, pneumaticactuators, screw-drive motors, stepper motors, and other known actuationmeans for controlling the movement of positioning element 140′ in such away as to cause support element 132′ to move from one elevation toanother in a substantially vertical direction and with a higher degreeof dimensional precision. Additionally, positioning element 140′ andactuation element 146′ may desirably elevate support element 132′ and,thus, each fabrication substrate 50 thereon out of chamber 110′ tofacilitate movement of each fabrication substrate 50 by substratehandling system 600 (FIGS. 1 and 2). Alternatively, the level at whichsurface 128 of volume 124 of unconsolidated material 126 is located maybe lowered below support surface 134′.

Control over the operation of actuation element 146′ and, thus, over themovement of positioning element 140′ and elevation of support element132′ may be provided by controller 700 or another processing element105′ (e.g., a processor or smaller collection of logic circuits), whichmay be dedicated for use with support system 130′ or fabrication tank100′, in communication therewith, either as a part of fabrication tank100′ or, more generally, as a part of stereolithographic apparatus 10,10′ (FIGS. 1 and 2).

Reservoir 120′ may include a surface level control element 150′ which isconfigured to maintain surface 128 of volume 124 of unconsolidatedmaterial 126 at a substantially constant elevation. Surface levelcontrol element 150′ may include a surface level sensor 152′ and anelement for adjusting volume 124 of unconsolidated material 126, whichelement is referred to herein as a “volume adjustment element” 154′.Both surface level sensor 152′ and volume adjustment element 154′ maycommunicate with controller 700 or processing element 105′, whichmonitors the level of surface 128, as indicated by signals produced andtransmitted by surface level sensor 152′, and facilitates adjustment ordisplacement of volume 124 by way of volume adjustment element 154′ tocompensate for changes in the elevation of surface 128 and therebymaintain surface 128 at a substantially constant elevation.

By way of example only, surface level sensor 152′ may comprise a lasersensor and reflected laser beam, which may be used in connection withone or more charge-coupled device (CCD) cameras or complementarymetal-oxide-semiconductor (CMOS) cameras. Triangulation techniques maybe used with such devices to determine the distance of surface 128 froma fixed point and, thus, the elevation, or level, at which surface 128is located.

If volume adjustment element 154′ is configured to change volume 124 ofunconsolidated material 126 within reservoir 120′, volume adjustmentelement 154′ may comprise a pump 156′ or series of pumps 156′ that mayremove unconsolidated material 126 from reservoir 120′ and transport thesame to an external reservoir 158′, as well as add unconsolidatedmaterial 126 from an external reservoir 158′ to reservoir 120′, as shownin FIG. 3C.

If volume adjustment element 154′ is instead configured to displace aportion of volume 124 located within reservoir 120′, volume adjustmentelement 154′ may, for example, comprise a piston or other displacementmember 160′ which may be incrementally introduced into and withdrawnfrom reservoir 120′, as shown in FIG. 3D. Of course, movement of such adisplacement member 160′ may be effected by an actuator 162′ therefor,such as a hydraulic actuator, a pneumatic actuator, a screw-drive motor,a stepper motor, or the like. Alternatively, vibrations may betransmitted directly to unconsolidated material 126 by, for example, apiston face, diaphragm, or the like.

Alternatively, as shown in FIG. 3E, a volume adjustment element 154″ mayinclude one or more apertures or other openings 102 in a side wall 101of fabrication tank 100′ that have lower edges 103 that are positionedat an elevation within fabrication tank 100′ at which surface 128 ofvolume 124 of unconsolidated material 126 is to be maintained. Inaddition, surface level control element 154″ includes one or morereceptacles 104 that communicate with openings 102 to receiveoverflowing unconsolidated material 126 as support element 132′ and asubstrate or other workpiece thereon, as well as anystereolithographically fabricated objects, are lowered into fabricationtank 100′ and displace unconsolidated material 126 therein. A pumpingsystem or other material recycling element 105 may communicate with eachreceptacle 104 in such a way as to return overflowed unconsolidatedmaterial 126 to tank 100′ as support element 132′ is raised tofacilitate stereolithographic fabrication of one or more other objects.

The introduction of support element 132′ or one or more fabricationsubstrates 50 into a volume 124 of unconsolidated material 126 containedwithin reservoir 120′ may result in the introduction of gas or airbubbles into unconsolidated material 126. Accordingly, referring againto FIG. 3, fabrication tank 100′ may optionally include a bubbleelimination system 165′ which is associated with a boundary or wall 114′of reservoir 120′ or with support system 130′ so as to facilitate theremoval of air or gas bubbles (not shown) from unconsolidated material126. By way of example, bubble elimination system 165′ may comprise anultrasonic transducer of a known type (e.g., a piezoelectrictransducer), which causes fabrication tank 100′ or support system 130′thereof to vibrate. Vibrations in fabrication tank 100′ or supportsystem 130′ are transmitted to unconsolidated material 126 withinreservoir 120′, causing any bubbles therein to dislodge from a structureto which they are adhered and float to surface 128, where they will popor may be removed, such as by use of negative pressure.

Referring now to FIG. 4, another exemplary embodiment of fabricationtank 100″ is illustrated. Fabrication tank 100″ includes a reservoir120″ at the base thereof and a chamber 110″ which is located overreservoir 120″ and which is continuous therewith. In addition, chamber110″ of fabrication tank 100″ includes a material reclamation zone 170″,as well as a cleaning zone 180″ located above material reclamation zone170″.

As shown, reservoir 120″ may be configured to contain a substantiallyconstant volume 124 of material, including unconsolidated material 126and, if stereolithographic processes have been initiated, consolidatedmaterial 126′ (FIG. 14). Accordingly, reservoir 120″ may include asurface level control element 150′, such as that described above inreference to FIGS. 3, 3C, and 3D.

A support system 130″ of fabrication tank 100″ includes a supportelement 132″ which is positionable at a plurality of distinct, preciseelevations within reservoir 120″ and, optionally, within chamber 110″.Movement of support element 132″ is effected by a positioning element140″. Positioning element 140″ is, in turn, associated with an actuationelement 146″, which may be actuated to cause positioning element 140″ tomove so as to position support element 132″ at a desired elevationwithin reservoir 120″ or chamber 110″. Additionally, positioning element140″ may elevate support element 132″ and, thus, any fabricationsubstrates 50 thereon out of chamber 110″ to facilitate handling offabrication substrates 50 by substrate handling system 600 (FIGS. 1 and2). Actuation element 146″ may communicate with controller 700 orprocessing element 105′ in such a way that controller 700 directs theoperation of actuation element 146″.

In addition, actuation element 146″ may be configured to rotate supportelement 132″ about an axis A thereof and within a plane P in whichsupport element 132″ is located. Alternatively, fabrication tank 100″may include a rotation element 148″ that is independent from actuationelement 146″ and which is configured to cause support element 132″ torotate. Such rotation may occur under instructions, in the form ofsignals or carrier waves, from controller 700 or processing element105′. By way of example and not by way of limitation, a stepper motor ora screw-drive motor that has been modified to move a screw, thenmaintain the screw in a substantially constant location when the screwhas reached one or more certain positions (e.g., material reclamationzone 170″ or cleaning zone 180″), may be used as either actuationelement 146″ or rotation element 148″.

When support element 132″ is moved into material reclamation zone 170″or cleaning zone 180″ of chamber 110″, actuation element 146″ orrotation element 148″ may cause support element 132″ to accelerate androtate at a sufficient speed that centrifugal force causes any excessunconsolidated material 126 and/or cleaning agents 127, such as water,solvents for unconsolidated material 126, detergents, combinationsthereof, or the like, to be removed from a fabrication substrate 50carried thereby while remaining substantially within the same plane asthat within which support element 132″ is located.

Material reclamation zone 170″ and cleaning zone 180″ may each beprovided with a receptacle 172″, 182″, respectively, that extendssubstantially around the periphery of an inner boundary or wall 114″ ofreservoir 120″. Receptacles 172″ and 182″ are each positioned atapproximately the same elevations within reservoir 120″ that supportelement 132″ will be located when positioned within reclamation zone170″ and cleaning zone 180″ thereof, respectively. Accordingly, asexcess unconsolidated material 126 and/or cleaning agents 127 areremoved, by spinning, from each fabrication substrate 50 that is carriedby support element 132″, receptacle 172″, 182″ will receivesubstantially all of the excess unconsolidated material 126 or cleaningagents 127 that are removed therefrom.

Since support element 132″ of fabrication tank 100″ is configured to berotated, or spun, at relatively high speed, support element 132″ may beconfigured to retain one or more fabrication substrates 50 during suchrotation, or spinning. FIGS. 4A and 4B depict an example of a retentionsystem 190 that may be used on a support element 132″ to secure afabrication substrate 50 in place thereon, particularly when supportelement 132″ is being accelerated to spin at high rotational speeds.

The depicted retention system 190 includes a raised periphery 191 thatforms a receptacle 192 within which a fabrication substrate 50 may besubstantially laterally contained. Thus, when support element 132″ isrotated, or spun, raised periphery 191 prevents a fabrication substrate50 that is being carried by support element 132″ from being thrownlaterally therefrom. One or more alignment features 193, which ensurethat fabrication substrate 50 has been properly positioned and orientedwithin receptacle 192, may also be formed by the inner border of raisedperiphery 191. In addition, retention system 190 may include one or moreaccess elements 194 which provide access to portions of an outerperiphery 55 of a fabrication substrate 50 located within receptacle192, thereby facilitating removal of fabrication substrate 50 fromreceptacle 192, as well as placement of another fabrication substrate 50therein.

Optionally, raised periphery 191 may protrude above an upper surface 56of fabrication substrate 50 a distance which comprises a maximumdistance a stereolithographically fabricated object (not shown) mayprotrude from upper surface 56. Unconsolidated material 126 that isintroduced onto upper surface 56 of fabrication substrate 50 may belaterally contained by raised periphery 191. An upper surface 22U′ ofthe uppermost layer 22′ of unconsolidated material 126 within theconfines of raised periphery 191 may be planarized by translating aplanarizing element 195, such as a meniscus blade (which includes ameniscus at the trailing edge thereof) or air knife, thereacross toremove unconsolidated material 126 and/or smooth upper surface 22U′. Anuppermost surface of raised periphery 191 defines the level at whichplanarizing element 195 may be translated across unconsolidated material126.

Raised periphery 191 may be an integral part of a support surface 134″of support element 132″, with the majority of retention system 190 beingformed in support surface 134″. Alternatively, retention system 190 maybe formed separately from the manufacture of support element 132″ andsecured to support surface 134″ thereof. By way of example only,stereolithographic processes may be employed to fabricate retentionsystem 190 on support surface 134″, such as by using stereolithographicapparatus 10.

Additionally, retention system 190 may include a sealing element 198,which may be positioned on support surface 134″ so as to underlie atleast a periphery of a fabrication substrate 50 positioned thereover. Byway of example only, sealing element 198 may comprise a somewhatflattened ring which is configured to seal against an outer periphery 55of fabrication substrate 50, as well as regions of bottom surface 51 offabrication substrate 50 which are located adjacent to outer periphery55. Such a sealing element 198 may prevent unconsolidated material 126from contacting bottom surface 51 of fabrication substrate 50 andsupport surface 134″ of support element 132″. Exemplary materials fromwhich sealing element 198 may be fabricated include, without limitation,compressible, resilient materials, such as silicone, polyurethane,ethylene vinyl alcohol (EVA), or the like.

Also, in order to secure fabrication substrate 50 in place relative tosupport surface 134″, retention system 190 may include one or morepressure ports 196, which are configured to communicate with a pressuresource 197 (e.g., a vacuum or an air compressor). As support element132″ is configured to be rotated, each pressure port 196 may be fittedwith a valve 199, which seals that pressure port 196 when pressuresource 197 is not in communication therewith. Of course, such valves 199are not necessary when support element 132″ does not rotate, as infabrication tank 100′. As a negative pressure is applied through the oneor more pressure ports 196 to a bottom surface 51 of fabricationsubstrate 50, the negative pressure pulls fabrication substrate 50against sealing element 198, sealing bottom surface 51 against sealingelement 198. In addition to securing fabrication substrate 50 oversupport surface 134″ and possibly providing a cushion for fabricationsubstrate 50, as noted previously, sealing element 198 may preventunconsolidated material from contacting bottom surface 51 and supportsurface 134″. Operation of pressure source 197 and, if necessary,communication thereof with pressure ports 196 may be under control ofcontroller 700, processing element 105′, or another processing elementthat is dedicated for use with retention system 190.

FIGS. 4C and 4D illustrate a variation of retention system 190′, whichis useful with support element 132″ of fabrication tank 100″. Retentionsystem 190′ includes one or more ejection elements 196′. Ejectionelements 196′ are useful for removing fabrication substrate 50 fromreceptacle 192, as well as for breaking a seal caused by the presence ofa negative pressure beneath fabrication substrate 50, which is appliedagainst at least a portion of bottom surface 51 thereof. Operation ofejection elements 196′ may be controlled by way of a controller 700 incommunication therewith. By way of example only, each ejection element196′ may comprise a mechanical piston that may be recessed withinsupport surface 134″ to facilitate placement of a fabrication substrate50 thereon or raised by an actuation element 197′ (e.g., a pneumatic,hydraulic, or mechanical actuation element) to protrude from supportsurface 134″ and eject a fabrication substrate 50 from receptacle 192and raise fabrication substrate 50 to facilitating grasping thereof bysubstrate handling system 600. In this example, it is actuation element197′ that communicates with controller 700, processing element 105′, oranother processing element and that operates in accordance withinstructive signals, or carrier waves, from controller 700, processingelement 105′, or the other processing element.

Alternatively, referring again to FIGS. 4A and 4B, each ejection element196′ may comprise a pressure port 196, which, as described previouslyherein, communicates with one or more pressure sources 197. A negativeair pressure may be applied through pressure port 196 to a bottomsurface 51 of a fabrication substrate 50 to secure the same to supportsurface 134″. Conversely, a positive air pressure may be forced throughport 196 against bottom surface 51 to eject a fabrication substrate 50from support surface 134″. As shown, each pressure source 197 maycommunicate with controller 700, processing element 105 ′, or anotherprocessing element (FIG. 4), which directs operation of pressure source197 by known means. The use of ejection element 196′ to apply positiveair pressure to bottom surface 51 of fabrication substrate 50 may alsobe used to break a seal, if any, between bottom surface 51 and afeature, such as a sealing element 198, of support element 132″.

Optionally, pressure ports 196 may be configured and the output ofpressure source 197 modulated so as to create a circulating airflowbeneath bottom surface 51 as positive pressure is forced therethrough,causing fabrication substrate 50 to be lifted off of support surface134″ in such a way as to hover thereover in accordance with Bernoulli'sLaw. Such an ejection element 196′ is, therefore, useful forfacilitating the grasping of fabrication substrate 50 by a substratehandling system 600 (FIGS. 1 and 2) of stereolithographic apparatus 10,10′, as well as to remove any unconsolidated material 126 from supportsurface 134″.

Another embodiment of support system 130′″ that may be used in afabrication tank 100, 100′, 100″ of a stereolithographic apparatus 10,10′ according to the present invention is shown in FIGS. 4E and 4F.Support system 130′″ includes a support element 132′″ and a locking ring191 ′″ that surrounds at least a portion of outer periphery 55 offabrication substrate 50 to secure the same to support element 132′″.Locking ring 191′″ forms a receptacle 192′″ within which fabricationsubstrate 50 is laterally contained. An upper surface 56 of fabricationsubstrate 50, however, remains substantially exposed.

Locking ring 191′″ includes an upper, laterally inwardly extending lip193′″ which is configured to contact an upper surface 56 of fabricationsubstrate 50. As locking ring 191′″ also defines a fixed distancebetween a support surface 134′″ and lip 193′″, which distance may not bethe same as the thickness of a fabrication substrate 50 to be positionedtherebetween, one or more spacers 194′″ may be fabricated (e.g.,stereolithographically) or positioned on support surface 134′″ so thatsupport system 130′″ may be tailored to accommodate thinner fabricationsubstrates 50. Spacers 194′″ are also useful for preventing bottomsurface 51 of fabrication substrate 50 from adhering to support surface134′″ of support element 132′″. Support elements 132′″ of this type,including stereolithographically fabricated support elements 132′″, maybe reused.

A thickness of lip 193′″ may define a maximum distance astereolithographically fabricated object (not shown) may protrude fromupper surface 56 of fabrication substrate 50. The thickness of lip 193′″may be increased by positioning or forming (e.g.,stereolithographically) an extension ring 202′″ thereon. Unconsolidatedmaterial 126 that is introduced onto upper surface 56 of fabricationsubstrate 50 may be laterally contained by lip 193′″. By way of exampleonly, unconsolidated material 126 may be introduced within the confinesof lip 193′″ and any extension rings 202′″ thereon by lowering supportsystem 130′″ beneath surface 128 (FIG. 4) of volume 124 ofunconsolidated material 126 so as to permit unconsolidated material 126to flow therein, then raising support system 130′″ so that an upper edgeof lip 193′″ or an extension ring 202′″ thereon is substantiallycoplanar with surface 128.

An upper surface 22U′ of the uppermost layer 22′ of unconsolidatedmaterial 126 within the confines of lip 193′″ and any extension rings202′″ thereon may be planarized by translating a planarizing element195, such as a meniscus blade or air knife, thereacross (FIG. 4B). Anuppermost surface of lip 193′″ or an extension ring 202′″ thereondefines the level at which planarizing element 195 may be translatedacross unconsolidated material 126.

Optionally, with returned reference to FIG. 4, fabrication tank 100″ mayinclude a bubble elimination system 165′, such as that described inreference to FIG. 3. Alternatively, stereolithographic fabrication tanks100, such as those that have chambers 110 with relatively small volumes(e.g., which are sufficient to contain only a single semiconductorsubstrate 52), may include bubble elimination systems that create anegative pressure, or vacuum, within the chambers thereof. Such a bubbleelimination system may, for example, include one or more sealingelements, which substantially seal chamber 110 of stereolithographicapparatus 10 (FIG. 1), as well as a negative pressure source thatcommunicates at least with chamber 110 so as to facilitate the creationof a negative pressure therein.

Turning now to FIG. 5, still another embodiment of fabrication tank100′″ that may be used in a stereolithographic apparatus 10, 10′ (FIGS.1 and 2) according to the present invention is shown. Fabrication tank100′″ includes substantially all of the same elements as the embodimentof fabrication tank 100″ described in reference to FIG. 4, except forreservoir 120″. Instead of an integral reservoir, such as reservoir120″, fabrication tank 100′″ includes a dispenser 120′″ for applyingunconsolidated material 126, which is drawn from an external reservoir159′″, to a fabrication substrate 50. By way of example only, dispenser120′″ may comprise a laminar flow dispenser or a spray nozzle of a knowntype. A laminar flow dispenser is currently preferred for use asmaterial dispenser 120′″, as laminar flow would result in the presenceof fewer air bubbles in unconsolidated material 126 than would bepresent if unconsolidated material 126 were sprayed onto fabricationsubstrate 50 and, thus, eliminate the need for removing such bubbles.Additionally, when dispensed with a laminar flow dispenser,unconsolidated material 126 may be applied to upper surface 56 offabrication substrate 50 without covering any structures that protrudetherefrom (e.g., solder balls that protrude from a semiconductor device54), thereby eliminating the need to subsequently remove consolidatedmaterial or unconsolidated material 126 from such structures. Dispenser120′″ may apply a predetermined quantity, or metered amount, ofunconsolidated material 126 onto fabrication substrate 50 to form asingle layer 22 or multiple layers 22 a, 22 b, etc. of unconsolidatedmaterial 126 thereon, which are to be sequentially dispensed and,possibly, sequentially consolidated.

Of course, operation of dispenser 120′″ may be controlled by controller700 or by a processing element 105′″ (e.g., a processor or smaller groupof logic circuits) that is associated with fabrication tank 100′″.

Material Consolidation System

Various exemplary embodiments of material consolidation systems 200(FIGS. 1 and 2) that may be used in a stereolithographic apparatus 10according to the present invention are shown in FIGS. 6 and 7.

With reference to FIGS. 1 and 6, a stereolithographic apparatus 10 thatincorporates teachings of the present invention may include a materialconsolidation system 200′ which is configured to direct a focused beamof consolidating energy, such as a laser beam 220′, into a chamber 110of a fabrication tank 100 and onto selected locations of a surface 128of a volume 124 of unconsolidated material 126 which is exposed tochamber 110.

When a laser beam 220′ is employed as the consolidating energy, materialconsolidation system 200′ includes a laser 210′ of a known type thatgenerates laser beam 220′. By way of example only, laser 210′ mayinclude a source 211 ′ which is configured to generate light in theultraviolet (UV) range of wavelengths of electromagnetic radiation.Laser 210′ may also include one or more lenses 216 to focus a laser beam220′ that has been emitted by source 211′ to a desired resolution. Alocation control element 212′, such as a scan controller (e.g., agalvanometer) of a known type, may be associated with source 211 ′ oflaser 210′ in such a way as to control the path of a laser beam 220′emitted from source 211′ and, thus, to effect movement of laser beam220′. The operation of location control element 212′ and, thus, themovement of a laser beam 220′, may be controlled by controller 700 or aprocessing element 205′ (e.g., a processor or smaller group of logiccircuits) which is dedicated for use with laser 210′, in accordance witha CAD program and an accompanying CAD file for the object to befabricated.

It is well known that the resolution of a laser beam 220′ that is to bemoved may be substantially maintained by keeping the path of laser beam220′ as constant (in this case, vertical) as possible. This may be doneby increasing the path length of that laser beam 220′ (e.g., to abouttwelve (12) feet). Nonetheless, it may not be practical for astereolithographic apparatus 10 (FIG. 1) that incorporates teachings ofthe present invention to include a laser 210′ with a source 211′ that ispositioned a sufficient distance from surface 128 of volume 124 ofunconsolidated material 126 that is to be selectively consolidated bylaser beam 220′. Accordingly, laser 210′ may also include a suitablemirror 214′ or series of mirrors 214′ that results in a nonlinear pathfor laser 210′ to provide a desired path length L for laser beam 220′ ina fixed amount of available space. As depicted, the area of mirror 214′may be large enough to substantially cover the entire cone of possibleangles at which laser beam 220′ may be directed by location controlelement 212′ and, thus, to reflect laser beam 220′ from every possibledirection onto a corresponding location of surface 128.

Optionally, or as an alternative to the use of a location controlelement 212′, the position and/or orientation of one or more of mirrors214′ may be moved, such as by an actuator 215′ therefor (e.g., a motor).The operation of actuator 215′ and, thus, the movement of a mirror 214′associated therewith, may be controlled by controller 700.

The size of the “spot” 222′ of a laser beam 220′ that impinges onsurface 128 of unconsolidated material 126 to consolidate (e.g., cure)the same may be on the order of about 0.001 inch to about 0.008 inchacross. It is currently preferred that, when laser beam 220′ is movedacross surface 128 (i.e., in the X-Y plane), the resolution of laserbeam 220′ be ±0.0003 inch over at least a 0.5 inch×0.25 inch field froma predetermined center point C on surface 128, thereby providing a highresolution scan across an area of at least 1.0 inch×0.5 inch. Of course,it is desirable to have substantially this high a resolution across theentirety of surface 128 to be scanned by laser beam 220′, such areabeing termed the “field of exposure.”

FIG. 7 depicts another exemplary embodiment of material consolidationsystem 200″, which is configured to direct unfocused, or blanket,consolidating energy 220″ in the form of electromagnetic radiation(e.g., light or a light beam) into a chamber 110 of a fabrication tank100 and onto a surface 128 of a volume 124 of unconsolidated material126 which is exposed to chamber 110.

A source 210″ of consolidating energy 220″ may remain in a fixedposition as consolidating energy 220″ is introduced into chamber 110 orsource 210″ may be moved, such as by an actuation system 217″ therefor.By way of example only, such an actuation system 217″ may comprise anX-Y plotter of a known type, which may operate and, thus, move source210″ under the direction of signals, or carrier waves, that have beentransmitted by controller 700 or by a processing element 205″ (e.g., aprocessor or smaller group of logic circuits) that controls operation ofmachine consolidation system 200″. Operation of source 210″ may be undercontrol of controller 700 or processing element 205″.

Of course, when unconsolidated material 126 is nonselectivelyconsolidated by consolidating energy 220″ from source 210″, a machinevision system 300 (FIGS. 1 and 2) is not employed at that time.

Machine Vision System

With returned reference to FIG. 1, a stereolithographic apparatus 10according to the present invention that employs a material consolidationsystem 200 (e.g., material consolidation system 200′ shown in FIG. 6)which selectively consolidates material 126 may also include a machinevision system 300. It is currently preferred that the field of vision ofmachine vision system 300 be substantially coextensive with the field ofexposure of a laser beam 220′ (FIG. 6) or other consolidating energy 220employed by a material consolidation system 200 to be used inconjunction with machine vision system 300.

Examples of different types of machine vision systems 300 that may beused in accordance with teachings of the present invention areillustrated in FIGS. 8 and 9.

In FIG. 8, a scanning embodiment of machine vision system 300′, or onewhich is configured to move relative to a chamber 110 of a fabricationtank 100 (FIGS. 1 and 2) with which it is used, is depicted. Machinevision system 300′ includes a camera 310′ which may be carried and movedover a fabrication substrate 50 by a scan element 312′. Scan element312′ positions camera 310′ in close proximity to (e.g., inches from)surface 128 (FIG. 1) of volume 124 of unconsolidated material 126(FIG. 1) so as to enable camera 310′ to view minute features on afabrication substrate 50 (e.g., bond pads, fuses, or other circuitelements of a semiconductor device) that is located at or near surface128. Upon viewing fabrication substrate 50, camera 310′ communicatesinformation about the precise locations of such features (e.g., with anaccuracy of up to about ±0.1 mil (i.e., 0.0001 inch)) to a computer 320′of machine vision system 300′.

Camera 310′ may comprise any one of a number of commercially availablecameras, such as CCD cameras or CMOS cameras available from a number ofvendors. Of course, the image resolution of camera 310′ should besufficiently high as to enable camera 310′ to view the desired featuresof fabrication substrate 50 and, thus, to enable computer 320′ toprecisely determine the positions of such features. In order to provideone or more reference points for the features that are viewed by camera310′, camera 310′ may also “view” one or more fiducial marks 112 withina chamber 110 (FIG. 1) of a fabrication tank 100 (FIG. 1) with whichmachine vision system 300′ is used.

Suitable electronic componentry, as required for adapting or convertingthe signals, or carrier waves, that are output by camera 310′, may beincorporated in a board 322′ installed in a computer 320′. Suchelectronic componentry may include one or more processors 324′, othergroups of logic circuits, or other processing or control elements thathave been dedicated for use in conjunction with camera 310′. At leastone processor 324′, which may include a processor, another, smallergroup of logic circuits, or other control element that has beendedicated for use in conjunction with camera 310′, is programmed, asknown in the art, to process signals that represent images that havebeen “viewed” by camera 310′ and respond to such signals.

A self-contained machine vision system available from a commercialvendor of such equipment may be employed as machine vision system 300′.Examples of such machine vision systems and their various features aredescribed, without limitation, in U.S. Pat. Nos. 4,526,646; 4,543,659;4,736,437; 4,899,921; 5,059,559; 5,113,565; 5,145,099; 5,238,174;5,463,227; 5,288,698; 5,471,310; 5,506,684; 5,516,023; 5,516,026; and5,644,245. The disclosure of each of the immediately foregoing patentsis hereby incorporated herein in its entirety by this reference. Suchsystems are available, for example, from Cognex Corporation of Natick,Mass. As an example, and not to limit the scope of the presentinvention, the apparatus of the Cognex BGA INSPECTION PACKAGE™ or theSMD PLACEMENT GUIDANCE PACKAGE™ may be adapted for use in astereolithographic apparatus 10 (FIG. 1) that incorporates teachings ofthe present invention, although it is currently believed that theMVS-8000™ product family and the Checkpoints product line, the latteremployed in combination with Cognex PATMAX™ software, may be especiallysuitable for use in the present invention.

A response by computer 320′ may be in the form of instructions regardingthe operation of a material consolidation system 200 (FIGS. 1 and 2),such as the selectively consolidating material consolidation system 200′shown in FIG. 6. These instructions may be embodied as signals, orcarrier waves. By way of example only, such responsive instructions maybe communicated to controller 700 of stereolithographic apparatus 10,10′ (FIGS. 1 and 2, respectively) or directly to a processing element205′ (FIG. 6), such as a processor or group of processors, associatedwith a material consolidation system 200 (FIGS. 1 and 2) (e.g., materialconsolidation system 200′ shown in FIG. 6) with which machine visionsystem 300′ is used. Controller 700 or processing element 205′ may, inturn, cause material consolidation system 200′ to operate in such a wayas to effect the stereolithographic fabrication of one or more objectson fabrication substrate 50 precisely at the intended locations thereof.

Due to the close proximity of camera 310′ to surface 128 (FIG. 1), thefield of vision of camera 310′ is relatively small. In order to enablecamera 310′ to view a larger area of surface 128 than that which is“covered” by or located within the field of vision camera 310′, a scanelement 312′ of a known type is configured to traverse camera 310′ overat least part of the area of surface 128. Scan element 312′ is alsouseful for moving camera 310′ out of the path of any selectivelyconsolidating energy being directed toward surface 128. By way ofexample only, scan element 312′ may comprise an X-Y plotter or scannerof a known type. Generally, an X-Y plotter or scanner includes an x-axiselement 313′ and a y-axis element 315′ that intersect one another. Asdepicted, camera 310′ is carried by both x-axis element 313′ and y-axiselement 315′ and, thus, is positioned at or near the location wherex-axis element 313′ and y-axis element 315′ intersect one another.

X-axis element 313′ and y-axis element 315′ are both configured to moverelative to and, thus, to position camera 310′ at a plurality oflocations over a fabrication substrate 50. Movement of x-axis element313′ is effected by an actuator 314′ (e.g., a stepper motor andactuation system, such as a gear or wheel that moves x-axis element 313′along a track) that has been operatively coupled thereto, with actuator314′ being configured to cause x-axis element 313′ to move laterally(i.e., perpendicular to the length thereof) along a y-axis. Y-axiselement 315′ is operatively coupled to an actuator 316′ therefor, whichis configured to cause y-axis element 315′ to move laterally along anx-axis. Actuators 314′ and 316′ may be configured to move theirrespective x-axis element 313′ and y-axis element 315′ in asubstantially continuous fashion or in an incremental fashion. Movementof actuators 314′ and 316′ may be controlled by a processing elementsuch as computer 320′ or a scanning controller 326′, such as a processoror smaller group of logic circuits, that is dedicated to operation ofscan element 312′ and which may communicate with computer 320′ in such away as to provide computer 320′ with information as to the specificlocation of camera 310′ relative to surface 128 (FIG. 1).

FIG. 9 shows an embodiment of machine vision system 300″ that includes acamera 310″ which is mounted or otherwise secured in a fixed positionrelative to surface 128 and may be maintained in a fixed positionrelative to a chamber 110 of a fabrication tank 100 (FIGS. 1 and 2) withwhich machine vision system 300″ is to be used. By way of example only,camera 310″ may be positioned in close proximity to a mirror 214′ ofmaterial consolidation system 200′ (FIG. 6) or at any other locationwhich will provide camera 310″ with a substantially unobstructed fieldof vision that covers the areas within which fabrication substrates 50may be located.

Like camera 310′, which is described in reference to FIG. 8, camera 310″may comprise a CCD camera, a CMOS camera, or any other suitable type ofcamera. As camera 310″ is positioned farther away from a fabricationsubstrate 50 to be viewed thereby, however, camera 310″ may have aneffectively larger field of vision than camera 310′. Of course, suitableoptical and/or digital magnification technology may be associated withcamera 310″ to provide the desired level of resolution. Further,although camera 310″ may be locationally stationary, a suitable gimbalsstructure with rotational actuators may be employed to point camera 310″at a specific location in the field of exposure with little actualrotational movement. Thus, camera 310″ may be used for both broad, or“macro,” vision and viewing and inspection of miniature features.

While machine vision system 300″ lacks a scan element, the remainingfeatures thereof may be the same as and operate in the same or a similarmanner to the corresponding features of machine vision system 300′,which is described in reference to FIG. 8.

Cleaning Component

Exemplary embodiments of cleaning components 400 that may be used with astereolithographic apparatus 10 that incorporates teachings of thepresent invention, shown in FIG. 1, are depicted in FIGS. 4, 10, and 11.

The embodiment of cleaning component 400′ shown in FIG. 4 is configuredto be used with a fabrication tank 100″ that is configured like the oneshown in FIG. 4. Cleaning component 400′ may include an initial materialremoval component 410′ which is configured to remove excessunconsolidated material 126 from a fabrication substrate 50,an-applicator 420′ which is configured to introduce one or more cleaningagents 127 (e.g., water, solvents, detergents, etc.) onto at least anexposed surface of fabrication substrate 50, and a secondary materialremoval component 430′ that removes cleaning agents 127 and any residualunconsolidated material 126 from fabrication substrate 50.

Initial material removal component 410′ of cleaning component 400′comprises support system 130″ of fabrication tank 100″, as well asmaterial reclamation zone 170″ of chamber 110″ and receptacle 172″ offabrication tank 100″. Support system 130″ and, in particular, actuationelement 146″ or rotation element 148″ thereof, is configured toaccelerate rotation of a fabrication substrate 50 carried thereby to arelatively high speed (e.g., about 50 to about 6,000 rpm) in such a waythat any unconsolidated material 126 thereon will be forced therefromunder centrifugal force along substantially the same plane as thatwithin which fabrication substrate 50 is located, into receptacle 172″,and prevented from falling into reservoir 120″.

Optionally, a protective cover 175 may be positioned beneath supportelement 132″ and over surface 128 of volume 124 of unconsolidatedmaterial 126. Of course, protective cover 175 is configured to be placedin the appropriate location in such a way as to avoid contact withpositioning element 140″. Accordingly, protective cover 175 may includetwo or more sections 175 a, 175 b, one or more of which is configured toaccommodate positioning element 140″ upon being moved into position.Each section 175 a, 175 b of protective cover 175 may, for example, bemoved into position in a hinged fashion (i.e., about hinges 177), asdepicted, or by horizontally sliding each section 175 a, 175 b intoposition. In order to move protective cover 175 into position, it may beoperably coupled with an actuator 176 (e.g., a motor). Operation ofactuator 176 and, thus, movement of protective cover 175 may be directedby controller 700 or by a processing element 178, such as a processor orsmaller group of logic circuits, that is dedicated for use with cleaningcomponent 400′.

As an alternative to forcing excess unconsolidated material 126 which isremoved from fabrication substrate 50 into receptacle 172″ by rotating,or spinning, unconsolidated material 126 may be caused to fall intoreservoir 120″ and, thus, captured directly thereby.

Once excess unconsolidated material 126 has been substantially removedfrom fabrication substrate 50, positioning element 140″ is moved toraise support element 132″ from material reclamation zone 170″ tocleaning zone 180″.

By way of example only, applicator 420′ may comprise a fixed or movablehigh-pressure spray nozzle or group of nozzles that form a spray head421′, which is in flow communication with a source 422′ of cleaningagent 127 (e.g., water, solvents for unconsolidated material 126,detergents, etc.). Applicator 420′ is configured to be oriented so as todirect one or more cleaning agents 127 into chamber 110″ of fabricationtank 100″ and onto an exposed surface of a fabrication substrate 50 thatis carried by support system 130″ and located within cleaning zone 180″of chamber 110″.

Applicator 420′ may be located in a fixed position relative tofabrication tank 100″ or carried by a movable element 424′, such as arobotic arm, which is configured to position applicator 420′ so as toorient the same toward fabrication substrate 50, as depicted in FIG. 4.

Controller 700 or one or more dedicated processing elements 426′ (e.g.,a processor, a smaller group of logic circuits, etc.) that communicatewith controller 700, may communicate with applicator 420′ and itsassociated movable element 424′, if any. Accordingly, operation ofapplicator 420′, including, without limitation, the orientation of sprayhead 421 ′ and the application of cleaning agent 127 onto a surface offabrication substrate 50, may be performed under the direction of eithercontroller 700 or a dedicated processing element 426′.

Like initial material removal component 410′, secondary material removalcomponent 430′ of cleaning component 400′ includes support system 130″of fabrication tank 100″. In addition, secondary material removalcomponent 430′ includes cleaning zone 180″ and receptacle 182″ thereofof chamber 110″. Support system 130″ and, in particular, actuationelement 146″ or rotation element 148″ thereof, is configured toaccelerate rotation of a fabrication substrate 50 carried thereby to asufficiently high speed (e.g., about 50 to about 6,000 rpm) so that anycleaning agents 127 or unconsolidated material 126 thereon will beforced therefrom along substantially the same plane as that within whichfabrication substrate 50 is located, into receptacle 172″, and preventedfrom falling into reservoir 120″.

Optionally, positive air pressure, which may be supplied by use of aso-called “air knife,” such as that depicted and described in referenceto FIG. 11, may be positioned over each fabrication substrate 50following the cleaning process to dry any residual cleaning agents 127therefrom.

A variation of cleaning component 400′ does not comprise part of afabrication tank 100″ but, rather, is separate therefrom so as tocompletely avoid the potential for contamination of unconsolidatedmaterial 126 within reservoir 120″ with excess unconsolidated material126 being removed from fabrication substrate 50 with cleaning agents127.

Turning now to FIG. 10, another exemplary embodiment of cleaningcomponent 400″ is depicted. Cleaning component 400″ includes a materialremoval component 410″ and a wash element 420″, as well as a supportelement 430″ upon which one or more fabrication substrates 50 aresupported while material removal component 410″ and wash element 420″perform their intended tasks.

Material removal component 410″, which is positioned external tofabrication tank 100″, may comprise one or more removal heads 412″,through which either a negative pressure (e.g., a vacuum) or a positivepressure (e.g., about 30 psi (which is typically not sufficient topuncture the skin of an operator of stereolithographic apparatus 10,10′) or higher pressures may be used and delivered by a so-called “airknife,” such as that manufactured by Secomak Ltd. of Middlesex, UnitedKingdom, at a sufficient velocity to overcome the adhesion ofunconsolidated material 126 from fabrication substrate 50 and, thus,remove unconsolidated material 126 from fabrication substrate 50) may beapplied to a fabrication substrate 50. Each removal head 412″ may besupported by a positioning element 414″, such as a robotic arm.Positioning element 414″ places removal head 412″ in sufficientproximity to one or more surfaces of a fabrication substrate 50 so thata negative pressure (e.g., a vacuum) or positive pressure applied tofabrication substrate 50 by removal head 412″ may respectively draw anyexcess unconsolidated material 126 on fabrication substrate 50 intoremoval head 412″ or blow any excess unconsolidated material 126 fromfabrication substrate 50. Alternatively, support element 430″ may betransported so as to move fabrication substrate 50 in proximity to oneor more removal heads 412″. Material removal component 410″ may be usedin combination with a bulk removal process, such as tipping or invertinga fabrication substrate 50 to permit unconsolidated material 126 to flowtherefrom.

As fabrication substrate 50 is brought in proximity to wash element 420″or wash element 420″ is brought into proximity to fabrication substrate50, support element 430″ may remain secured to fabrication substrate 50.As shown, wash element 420″ may include one or more spray heads 421″that communicate with a source 422″ of cleaning agent 127 and which maybe oriented to direct cleaning agent 127 onto fabrication substrate 50.

Any cleaning agent 127 that remains on fabrication substrate 50 may beremoved therefrom by way of one or more removal heads 412″, which mayinclude at least one removal head 412″ that was used to remove excessunconsolidated material 126 from fabrication substrate 50 or a differentremoval head 412″.

Another embodiment of cleaning component 400′″ that may be used in astereolithographic apparatus 10, 10′ (FIGS. 1 and 2, respectively)according to the present invention is shown in FIG. 11. Cleaningcomponent 400′″ includes a tank 440′″ which is at least partially filledwith one or more cleaning agents 127 and within which one or morefabrication substrates 50 may be introduced, such as by the illustratedwafer boat 450′″. Additionally, cleaning component 400′″ may include anagitation system 460′″, which facilitates the removal of residualunconsolidated material from fabrication substrates 50. By way ofexample only, agitation system 460′″ may include a vertical agitationsystem, which repeatedly moves a support 452′″ upon which wafer boat450′″ is carried up and down.

As another alternative, a rotary wash system (not shown), such as thatavailable from Semitool of Kalispell, Mont., may be used to remove anyresidual unconsolidated material from one or more fabricationsubstrates.

Material Reclamation System

Again referring to FIGS. 4 and 10, an exemplary embodiment of materialreclamation system 500, shown in FIG. 1, is illustrated.

As depicted in FIG. 4, material reclamation system 500 includes acollection conduit 510 which includes a first end 512 that communicateswith receptacle 172″ of cleaning component 400′ so as to receive excessunconsolidated material 126 which has been collected by receptacle 172″.When used with the embodiment of cleaning component 400″ that is shownin FIG. 10, first end 512 of collection conduit 510 communicates withmaterial removal component 410″, such as a negative pressure head, so asto collect excess unconsolidated material 126 that has been drawn intomaterial removal component 410″.

The opposite, second end 514 of collection conduit 510 communicates witheither reservoir 120′, 120″, as shown, or an external reservoir 158′(FIG. 3C) in communication therewith. Accordingly, unconsolidatedmaterial 126 may be returned to reservoir 120′, 120″, or 158′ throughcollection conduit 510.

One or more filters 530, which are configured to permit the passage ofunconsolidated material 126 therethrough while trapping particulatecontaminants that are larger than a selected size, may also bepositioned along the length of collection conduit 510 or at an end 512,514 thereof.

One or more pumps 520 (e.g., peristaltic pumps) may communicate withcollection conduit 510, each applying either a positive or negativepressure thereto, to facilitate the transport of unconsolidated material126 therethrough, as well as the return of unconsolidated material 126to reservoir 120′, 120″, 158′ through conduit 510.

Calibration of the Programmed Material Consolidation Apparatus

With returned reference to FIGS. 1, 2, and 6, as well as with referenceto FIG. 12, machine vision system 300 (e.g., either a movable machinevision system 300′, such as that shown in FIG. 8, or a stationarymachine vision system 300″, such as that shown in FIG. 9) may be used tocalibrate stereolithographic apparatus 10, 10′ and, more particularly,material consolidation system 200 (e.g., the selective materialconsolidation system 200′ shown in FIG. 6) thereof Various types ofcalibration may be effected, including, but not limited to, calibrationof the position (X-Y) at which a selectively consolidating energy, suchas laser beam 220′, impinges upon surface 128 of volume 124 ofunconsolidated material 126, calibration of the magnification of machinevision system 300 and required movement of the selectively consolidatingenergy to effect fabrication of a structure of desired dimensions, andcalibration of the “squareness” of a grid of locations at which theselectively consolidating energy impinges upon surface 128.

The position at which selectively consolidating energy impinges uponsurface 128 may, by way of example only, be calibrated by selectivelyconsolidating unconsolidated material 126 at one or more calibrationlocations, each of which is referred to herein as a “reference pixel”750, on surface 128. Next, each reference pixel 750 is “viewed” bymachine vision system 300 to locate the same relative to a referencegrid (not shown), which may be stored in memory of either computer 320′(FIG. 8) or controller 700 (FIG. 1). The location at which eachreference pixel 750 actually appears is then compared with theanticipated location 750′ for reference pixel 750. Materialconsolidation system 200, the reference grid, or a combination of bothmay then be adjusted, as known in the art, to compensate for anydifference between anticipated location 750′ and the actual location ofreference pixel 750.

The magnification with which a movable machine vision system 300′, suchas that shown in FIG. 8, views objects that are located within orexposed to chamber 110 may be determined by moving camera 310′ a fixeddistance and determining the number of reference pixels 750 that are“viewed” (e.g., as changes in contrast sensed by camera 310′) as camera310′ is moved. For example, if camera 310′ is moved a linear distance of10 mils (i.e., 0.010 inch) and twenty (20) pixel widths (e.g., ten (10)pixels, each positioned one pixel width apart from each other) aredetected (e.g., as nineteen (19) changes, or transitions, in contrast),camera 310′ is magnifying a viewed image by a value which equates to a20:1 pixels-per-mil ratio. This process may then be repeated at leastonce to check the measured magnification of camera 310′. Knowledge ofthe pixel-to-mil ratio is useful for controlling the movement ofselectively consolidating energy, such as by controlling operation of alocation control element 212′ (e.g., pulsing of a stepper motor thatmoves a galvanometer) that moves a laser beam 220′ (FIG. 6).

A calibration plate (not shown) of a known type, which, of course, isconfigured specifically for the type of apparatus to be calibrated, maybe used to determine the magnification with which a fixed camera 310″ ofmachine vision system 300″, shown in FIG. 9, views objects that arelocated within or exposed to chamber 110. The calibration plate, whichis also referred to as a “prime standard,” includes features of knowndimensions and locations. These known dimensions may be compared, asknown in the art, with the image viewed by camera 310″ to determine thedegree to which an image of these features is magnified or demagnifiedby camera 310″.

The linearity with which selectively consolidating energy impinges uponsurface 128 across the field of exposure of material consolidationsystem 200′ may be determined and calibrated by determining the actuallocations 760 (FIG. 13), particularly at the corners and edges of arectangular field of exposure, at which selectively consolidatingenergy, such as laser beam 220′, impinges on surface 128. The actuallocations 760 at which the selectively consolidating energy impinges onsurface 128 may then be compared to locations 760′ (FIG. 13) that areanticipated if the selectively consolidating energy were impinging onsurface 128 in a linear path. Responsive to this comparison, movement ofthe selectively consolidating energy may be adjusted, or calibrated, insuch a way as to increase the linearity of the path along which theselectively consolidating energy impinges on surface 128 and, thus, theaccuracy with which the selectively consolidating energy impinges onsurface 128, particularly at the corners and edges of the field ofexposure. In the example of a laser beam 220′, adjustments in themovement thereof may be effected by adjustments in the manner in whichlocation control element 212′ (FIG. 6), such as a pair of galvanometers,are moved.

With reference to FIG. 13, such linearity calibration may be effected bypositioning light-sensitive elements 770, such as phototransistors, CCDarrays, or CMOS arrays, at selected locations within chamber 110, suchas at the four corners 116 thereof and along the edges 118 thereof,midway between two corners 116. Alternatively, a light-sensitive plate(not shown) of a known type (e.g., a large phototransistor, CCD array,or CMOS array) may be positioned within chamber 110 at an elevationwhich is substantially the same as that at which surface 128 (FIG. 6) isto be maintained during stereolithographic fabrication. As anotheralternative, reference pixels 750 may be formed by use of materialconsolidation system 200′ (FIG. 6) and viewed by machine vision system300, 300′, 300″ (FIGS. 1, 2, 8, and 9).

Use of the Programmed Material Consolidation Apparatus

In reference again to FIGS. 1 and 2, as well as to FIG. 14, an exampleof the use of a programmed material consolidation apparatus, such asstereolithographic apparatus 10, 10′, that incorporates teachings of thepresent invention is described.

In order to stereolithographically fabricate one or more objects 20,corresponding data from the .stl files, which comprise a 3D CADsimulation or model, resident in memory (e.g., random-access memory(RAM)) associated with controller 700 are processed by controller 700.The data, which mathematically represents the one or more objects to befabricated, may be divided into subsets, each subset representing alayer 22, or “slice,” of the object 20. The division of data may beeffected by mathematically sectioning the 3D CAD model into at least onelayer 22, a single layer or a “stack” of such layers 22 representing theobject 20. Each slice may be from about 0.0001 inch to about 0.0180 inchthick. A thinner slice promotes higher resolution by enabling betterreproduction of fine vertical surface features of the object or objectsto be fabricated.

Before fabrication of a first layer 22 a of an object 20 is commenced,the operational parameters for stereolithographic apparatus 10, 10′ maybe set to adjust the size (diameter if circular) of selectivelyconsolidating energy (e.g., laser beam 220′ shown in FIG. 6), if such isused to at least partially consolidate unconsolidated material 126.

In addition, controller 700 may automatically check and, if necessary,adjust by means known in the art the elevation, or level, of surface 128of volume 124 of unconsolidated material 126 to maintain the same at anappropriate focal length for laser beam 220′. U.S. Pat. No. 5,174,931,the disclosure of which is hereby incorporated herein in its entirety bythis reference, discloses an example of a suitable level control system.Alternatively, the height of a mirror 214′ (FIG. 6) that reflects laserbeam 220′ onto an appropriate location of surface 128 may be adjustedresponsive to a detected elevation of surface 128 to cause the focalpoint of laser beam 220′ to be located precisely at surface 128,although this approach is more complex.

A support system 130, 130′, 130″, 130′″ upon which one or morefabrication substrates 50 (e.g., semiconductor substrates 52) arecarried may then be submerged in unconsolidated material 126 withinreservoir 120, 120′, 120″ to a depth equal to the thickness of one layer22 or slice of the object 20 to be formed so as to form a layer 22′ ofunconsolidated material 126 on fabrication substrate 50. The elevationof surface 128 may subsequently be readjusted, as required toaccommodate any differences between unconsolidated material 126 andconsolidated material 126′. Alternatively, a layer 22′ of unconsolidatedmaterial 126 may be disposed onto an exposed upper surface 56 offabrication substrate 50.

A machine vision system 300, 300′, 300″ (FIGS. 1 and 2, 8, and 9,respectively) may then be used to view fabrication substrate 50 and toidentify each location thereof over which an object 20 is to befabricated.

Laser 210′ (FIG. 6) may then be activated so laser beam 220′ will scansurface 128 of volume 124 of unconsolidated material 126 so as to atleast partially consolidate (e.g., polymerize to an at least semisolidstate) the same, thereby defining boundaries of a layer 22 of object 20and filling in solid portions thereof. Support system 130, 130′, 130″,130′″ may then be lowered to lower fabrication substrate 50 a distancethat is substantially equal to the desired thickness of the next layer22 of object 20 to be fabricated thereover, and the selectiveconsolidation process repeated, as often as necessary, layer by layer,until each object 20 is completed. Of course, the number of layers 22that are required to form object 20 may depend upon the height of object20 and the desired thickness for each layer 22 thereof. Different layers22 of a stereolithographically fabricated object 20 may have differentthicknesses.

If desired, an uppermost layer 22U′ of unconsolidated material 126 maybe planarized, for example, by use of a planarizing element 195, such asthat described in reference to FIG. 4B. Planarizing elements 195 areparticularly useful when one or more layers 22′ of unconsolidatedmaterial 126 are dispensed over fabrication substrate 50 rather thanbeing formed thereover by submersion.

With continued reference to FIG. 14, as well as to FIG. 7,unconsolidated material 126 layer 22′ may be consolidated with lessselectivity by exposing layer 22′ to laser beam 220′ which has beenemitted from laser 210′ (not shown).

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention, butmerely as providing illustrations of some of the presently preferredembodiments. Similarly, other embodiments of the invention may bedevised which do not depart from the spirit or scope of the presentinvention. Moreover, features from different embodiments of theinvention may be employed in combination. The scope of the invention is,therefore, indicated and limited only by the appended claims and theirlegal equivalents, rather than by the foregoing description. Alladditions, deletions, and modifications to the invention, as disclosedherein, which fall within the meaning and scope of the claims are to beembraced thereby.

1. A method for calibrating a programmable material consolidationapparatus, comprising: viewing at least one location substantially at aconsolidation elevation of a fabrication site of the programmablematerial consolidation apparatus from a location above the consolidationelevation; evaluating data obtained from viewing the at least onelocation; and determining an amount of adjustment to be made to at leastone component of the programmable material consolidation apparatus, inresponse to the act of evaluating.
 2. The method of claim 1, whereinviewing is effected substantially at the consolidation elevation.
 3. Themethod of claim 1, wherein evaluating comprises comparing the data to atleast one expected data value.
 4. The method of claim 1, whereindetermining comprises determining that no adjustment of the at least onecomponent need be made.
 5. The method of claim 1, further comprising:adjusting the at least one component by the amount of adjustment.
 6. Themethod of claim 1, further comprising: adjusting the at least onecomponent of the programmable material consolidation apparatus by atleast a portion of the amount of adjustment.
 7. The method of claim 1,further comprising: fabricating at least one feature substantially atthe consolidation elevation.
 8. The method of claim 7, wherein viewingcomprises viewing the at least one feature.
 9. The method of claim 8,wherein fabricating includes fabricating a plurality of reference pixelssubstantially at the consolidation elevation.
 10. The method of claim 9,wherein evaluating data comprises comparing actual locations of theplurality of reference pixels to anticipated locations for the pluralityof reference pixels.
 11. The method of claim 10, further comprising:adjusting reference grid data by at least a portion of the amount ofadjustment.
 12. The method of claim 10, further comprising: adjusting amaterial consolidation element of the programmable materialconsolidation apparatus by at least a portion of the amount ofadjustment.
 13. The method of claim 12, further comprising: adjustingreference grid data by at least a portion of the amount of adjustment.14. The method of claim 1, wherein viewing comprises moving a viewpointfrom which viewing is effected along a path of a plurality of spacedapart reference pixels, each having a common, known dimension.
 15. Themethod of claim 14, further comprising: positioning a calibration plateincluding the plurality of spaced apart reference pixels substantiallyat the consolidation elevation.
 16. The method of claim 14, whereinmoving is effected substantially linearly.
 17. The method of claim 14,wherein viewing further comprises detecting transitions in contrast. 18.The method of claim 14, wherein viewing further comprises determining anumber of reference pixels viewed as the viewpoint is moved a particulardistance.
 19. The method of claim 18, wherein evaluating data comprisesevaluating the particular distance, the number of reference pixelsviewed, and the common, known dimension of the reference pixels todetermine a magnification at the viewpoint.
 20. The method of claim 19,further comprising: repeating the acts of moving, viewing, andevaluating at least once to verify the magnification at the viewpoint.21. The method of claim 19, further comprising: using the magnificationat the viewpoint to control operation of a material consolidationelement of the programmable material consolidation apparatus.
 22. Themethod of claim 1, further comprising: directing selectivelyconsolidating energy toward a plurality of locations of theconsolidation elevation.
 23. The method of claim 22, wherein directingincludes directing the selectively consolidating energy toward at leastone location proximate a corner or an edge of a rectangular field ofexposure at the consolidation elevation.
 24. The method of claim 22,wherein at least some of the plurality of locations are in substantiallylinear alignment.
 25. The method of claim 22, wherein viewing comprisesviewing actual locations of the consolidation elevation to which theselectively consolidating energy is directed.
 26. The method of claim25, further comprising: placing at least one light-sensitive elementsubstantially at the consolidation elevation, the viewing being effectedwith the at least one light-sensitive element.
 27. The method of claim25, wherein evaluating data comprises comparing the actual locations toanticipated locations of the consolidation elevation where selectivelyconsolidating energy was expected to be directed.
 28. The method ofclaim 22, further comprising: adjusting a material consolidation elementof the programmable material consolidation apparatus by at least aportion of the adjustment amount to increase a linearity of a path ofconsolidating energy generated by the material consolidation element.29. A calibration system for use with a programmable materialconsolidation apparatus, comprising: at least one imaging elementconfigured to be positioned above a consolidation elevation of theprogrammable material consolidation apparatus; and a controller incommunication with the at least one imaging element and programmable toeffect at least one calibration program that facilitates adjustment ofat least one feature of the programmable material consolidationapparatus to calibrate the same.
 30. The calibration system of claim 29,wherein the at least one imaging element comprises a machine visionsystem associated with the programmable material consolidationapparatus.
 31. The calibration system of claim 29, wherein the at leastone imaging element comprises at least one light-sensitive elementconfigured to be positioned at a location of the programmable materialconsolidation apparatus at which material consolidation is to occur. 32.The calibration system of claim 31, wherein the at least onelight-sensitive element is positioned at corners or edges of a field ofexposure of the programmable material consolidation apparatus.
 33. Thecalibration system of claim 31, comprising a plurality oflight-sensitive elements.
 34. The calibration system of claim 29,further comprising: a calibration plate including reference featuresthereon, the calibration plate being configured for placement at alocation of the programmable material consolidation apparatus at whichmaterial consolidation is to occur.
 35. The calibration system of claim29, further comprising: at least one actuator for moving the at leastone imaging element to a plurality of locations above the consolidationelevation.